1. Field of the Invention
The present invention relates to a mobile communications system, and particularly, to a periodic positioning method in a Secure User Plane Location (SUPL) based position information system.
2. Background of the Invention
In general, a mobile communications system has a function unit related to calculating of position of a mobile communications terminal (referred to as just a ‘terminal’ hereafter) in a mobile communications network, and thus provides location services for transferring the location (position) of the terminal to a certain entity periodically or according to a user's request.
Networks related to the location services have different structures according to an inner network structure of 3GPP or 3GPP2. The position of the terminal can be calculated using a cell-ID method for transferring a cell ID to which the terminal belongs, a method in which a time taken by transferring a radio wave from a terminal to each base station is calculated and a location (position) of the terminal is then calculated using a triangulation, a method using a Global Positioning System (GPS), and the like.
However, in order to provide location services to a user using the position calculation (positioning) method, considerable signaling and position information should be sent and received between the terminal and a location server. The so-called positioning technologies that have been standardized for providing such location services, namely, a location service based upon the location (position) of a terminal, are undergoing rapid widespread dissemination. The technologies can typically be provided through a user plane and a control plane. A Secure User Plane Location (SUPL), which is well-known as an example of the positioning technologies, provides the location services through the user plane
The SUPL is an efficient method for transferring location (position) information required for the positioning of a terminal. The SUPL protocol transfers positioning assistance information such as Global Positioning System (GPS) assistance. The SUPL employs a user plane data bearer to carry positioning technology associated protocols between the mobile terminal and a network.
In general, in a positioning system, a SUPL network related to a location service roughly includes a SUPL agent, SUPL Location Platform (SLP) and SUPL Enabled Terminal (SET). The SUPL agent denotes a logical service access point using position information which is actually measured. The SLP denotes a SUPL service access point within a network portion where network resources are accessed to obtain position information. The SET denotes a device for communicating with the SUPL network using a SUPL interface. The SET may denote, for instance, one of a User Equipment (UE) of UMTS, a Mobile Station (MS) of GSM, an IS-95 MS, a laptop computer having a SET function, Personal Digital Assistances (PDAs) or the like. The SET may also denote various terminals which access through a Wideband LAN (WLAN).
The SET supports various procedures defined by the SUPL by being connected to the network through the user plane bearer. Here, a network that a user has originally registered is referred to as a home network. When a user moves and thus is located at another area which is not in the home network area, the corresponding area is referred to as a visited network. The SLP within the home network is called as a Home-SLP (H-SLP), and the SLP within the visited network is called as a Visited-SLP (V-SLP). Here, upon initiating a SUPL procedure at the network, an SLP to which an external client is initially connected is referred to as a Requesting SLP (R-SLP). The R-SLP is a logical entity which may be either the same as the H-SLP or not. In addition, a SET which is a target for a current positioning (i.e., location tracking) is defined as a target SET.
The SLP, as a network element, may include a SUPL Positioning Center (SPC) which is an entity for calculating an actual position, and a SUPL Location Center (SLC) which manages functions of the SLP other than calculating location (position) information, for example, functions of roaming and resource management. Therefore, the SET may calculate the position information (i.e., perform positioning) through a communication with the SPC via the SLC (i.e., proxy mode), and may calculate the position information (i.e., perform positioning) by being directly connected to the SPC (i.e., non-proxy mode).
The SUPL based immediate positioning method has been disclosed in the elated art, however, a SUPL based periodic positioning methods has not been proposed therein.